Native bridge metadata message support for Podcast Image URL

[fdocr]

What type of PR is this? (check all applicable)

• [ ] Refactor
• [x] Feature
• [ ] Bug Fix
• [ ] Documentation Update

Description

The locked screen controls when playing a Podcast were showing the App Icon (poorly) for all Podcasts. This PR implements the code necessary to handle a URL sent in the metadata message. If no URL is received (or an invalid URL for that matter) the behavior is the same as before but slightly better.

Related Tickets & Documents

Implements the iOS side for #218

Mobile & Desktop Screenshots/Recordings (if there are UI changes)

Before:

With this PR & no Podcast Image received:

With this PR & valid Podcast Image received:

Added to documentation?

• [ ] docs.dev.to
• [ ] readme
• [x] no documentation needed